Summary:
Similar to the ARM target in https://reviews.llvm.org/rL298380, this
patch adds identical infrastructure for disabling negative immediate
conversions, and converts the existing aliases to the new infrastucture.
Reviewers: rengolin, javed.absar, olista01, SjoerdMeijer, samparker
Reviewed By: samparker
Subscribers: samparker, aemerson, llvm-commits
Differential Revision: https://reviews.llvm.org/D31243
llvm-svn: 298908